Living in South East Asia cell phone ‘plans’ are a bit different then they are in the States. Here you can buy ‘top-up’ cards for certain amounts for a set amount of data and use data on a continual basis as long as you keep ‘toping up’. This can be quite convenient and easy to use and cheaper than set plans. However, its somewhat difficult to track data usage without calling a 3 digit number all the time. This is where the phone app comes in.
Two apps that I’ve stumbled upon recently are Data Widget and Data Usage Pro. Both apps are $1.99, but I happen to get them for free. (Data Usage Pro currently is still free at the time of this writing).